A search engine provides assistance for matching a user's intent to a topic both at the time of query formulation and following submittal of a query. The former assistance often takes the form of auto-completion of a query during query formulation. The latter assistance often takes the form of post-submittal query suggestions. Such a query suggestion is least useful when it yields the same search results that the user has explored already.
Typically, a search engine selects candidates for post-submittal query suggestions based on query frequencies. The search engine then eliminates candidates that would result in co-clicks on similar uniform resource locators (URLs). While this approach is defensible as being consistent with a correct utility model, it is reactive rather than proactive.